Step 1: Understanding the Concept:
The Tarai region is a moist sub-Himalayan alluvial belt located immediately south of the Bhabhar gravelly foothills across northern and eastern India.
Step 2: Detailed Explanation:
Tarai soils occupy the wet, marshy, foot-hill plain tract stretching across Uttarakhand (Pantnagar/Udham Singh Nagar), northern Uttar Pradesh, northern Bihar, and West Bengal (Duars).
These soils are deep, rich in organic matter, highly fertile, fine-to-medium textured, and characterized by high water tables, making them intensively cultivated for sugarcane, paddy, and wheat.
Step 3: Final Answer:
Thus, Tarai soils are found in Uttarakhand, Uttar Pradesh, Bihar and West Bengal, matching option (A).